Host plant resistance to pest insects
Dr Rosemary Collier
VeGIN meeting 05 November 2009
Host plant resistance to pest
insects
Lettuce
Rosemary Collier
Nasonovia ribisnigri – currant lettuce
aphid
• Major pest aphid
of lettuce in
northern Europe
Aphid life cycles
Life cycle of the currant-lettuce aphid
Currant/gooseberry
Lettuce
• Increasing
problem in other
parts of the world
Life cycle: aphids on lettuce
Life cycle: currant lettuce aphid on
currant and lettuce
Percent plants infested
Foliage aphids - HRI Wellesbourne 1996
100
80
60
40
20
0
A
M
J
J
A
S
O
1
Host plant resistance to pest insects
Dr Rosemary Collier
VeGIN meeting 05 November 2009
Insecticide resistance – early studies
• Cypermethrin - wide range, up to at least 10-fold
resistance.
• Heptenophos - more uniform, within range for
standard strains (up to 4-fold resistance).
• Pirimicarb - all field strains ‘resistant’, magnitude
varied, some more than 11-fold resistant (4 to19fold in SW Europe).
Defra project - percent mortality with diagnostic doses
Date
Origin
Imidacloprid
(10ppm)
Pirimicarb
(100ppm)
Pymetrozine
(50ppm)
Lambdacyhalothrin
(2.5ppm)
Treatment
Sept'03
Lincs
100
100
30
100
Gaucho (seed), Dovetail, Plenum,
Nicotine
July'04
Sussex
100
Gaucho (seed), Dovetail, Plenum,
Nicotine, Hallmark
Aug'04
Sussex
100
100
85
92
Thiacloprid, Nicotine, Cypermethrin
Sept'04
Cambs
100
100
78
96
None (organic)
Sept'04
Lancs
85
100
94
88
None (organic)
Nov'04
Lincs
93
100
53
77
Sept'05
Cambs
100
97
90
83
Unknown
Sept'05
Lincs
100
100
100
100
Gaucho (seed), Dovetail, Aphox, Nicotine
Sept'05
Lincs
100
97
97
94
Oct'05
Worcs
100
100
90
100
Gaucho (seed), Plenum, Aphox
Oct'05
Worcs
100
93
80
93
Gaucho (seed) Plenum, Aphox, Stalwart
100
96
88
Unknown
Gaucho (seed), Plenum, Dovetail
• Imidacloprid - no evidence of resistance.
Cultivars resistant to lettuce aphid
• Range of cultivars available with full resistance to N.
ribisnigri
• 2007 – evidence that host plant resistance had been
broken in continental Europe
Facilities/techniques
• Aphid cultures – several clones
(insecticide susceptible, insecticide
resistant) plus host-plant resistance
breaking biotype
• 2008 – evidence that resistance broken in UK
• 2009 – we have collected some resistance-breaking
aphids for a PhD project – Gemma Hough – funded
by HDC – and to screen in this Defra project
Facilities for tests:
• Techniques to produce overwintering
eggs
Monitoring
• Glasshouses
• Open plots
• Small cages
• Controlled
environment rooms
Suction trap network
Rothamsted Research
2
Host plant resistance to pest insects
Dr Rosemary Collier
VeGIN meeting 05 November 2009
Diamond-back moth - Plutella xylostella
• World-wide pest of brassica crops
• Can complete its life-cycle rapidly in
warm weather – more generations,
more damage
Brassicas
• Insecticide resistant strains selected
very rapidly – harder to control
• Migrates into UK and causes damage
• Cannot survive UK winters at present
• But this may change…………
Climate change projections – diamond-back
moth – number of generations per year
Camborne Cornwall
base
2020s
2050s
2080s
Moths over-winter
first sighting 1 Feb
Kirton Lincolnshire
150
150
100
100
100
100
50
50
50
0
Frequency of synthetic years
2 3
4 5
6 7 8
9 10 11
50
0
2 3 4
5 6
7 8 9 10 11
0
2 3 4
5 6 7
8 9 10 11
150
150
150
150
100
100
100
100
50
50
50
0
0
2 3
Moths migrate in
first sighting 1 June
Leuchars Fife
150
0
Moths migrate in
first sighting 1 May
Wye Kent
150
4 5
6 7 8
9 10 11
5 6
7 8 9 10 11
5 6 7
8 9 10 11
150
150
150
100
100
100
100
50
50
50
0
2 3
Harcourt (1954)
4 5
6 7 8
9 10 11
5 6
7 8 9 10 11
5 6 7 8
9 10 11
2
3 4
5 6 7 8
9 10 11
2
3 4
5 6 7 8
9 10 11
50
0
2 3 4
3 4
0
2 3 4
150
0
2
50
0
2 3 4
Cauliflower in India devastated by diamond-back
moth despite 50 applications of insecticides
0
2 3 4
5 6 7
8 9 10 11
Number of generations before either the first Autumnal frost or 31 December
Cauliflower inoculated with 25 DBM
Wild brassicas
Control
Bt Cauliflower
(Cry 1B + Cry 1C)
3
Host plant resistance to pest insects
Dr Rosemary Collier
VeGIN meeting 05 November 2009
Resources and facilities
Other Brassica pests in culture
• Insect rearing unit
• Field plots, field cages
•
•
•
•
• Facilities to investigate mechanisms of
resistance – behaviour and ‘chemical’ analyses
• Accessible in field – whitefly, flea beetle,
pollen beetle, other Lepidoptera
Other crops - carrot
Other crops - alliums
• Resistance to carrot fly (Psila rosae)
• Resistance to thrips (+ other pests)
• Field population
• Wild population/greenhouse culture
• Can screen varieties/breeding lines
• Can screen varieties/breeding lines
• Investigate mechanisms of resistance
• Investigate mechanisms of resistance
• Glasshouses
Cabbage root fly (Delia radicum)
Cabbage aphid (Brevicoryne brassicae)
Peach-potato aphid (Myzus persicae)
Large white butterfly
4